On Thu, Jan 04, 2018 at 06:24:33PM +0000, Punit Agrawal wrote:
> KVM only supports PMD hugepages at stage 2 but doesn't actually check
> that the provided hugepage memory pagesize is PMD_SIZE before populating
> stage 2 entries.
>
> In cases where the backing hugepage size is smaller than PMD_SIZE (such
> as when using contiguous hugepages),
what are contiguous hugepages and how are they created vs. a normal
hugetlbfs? Is this a kernel config thing, or how does it work?
> KVM can end up creating stage 2
> mappings that extend beyond the supplied memory.
>
> Fix this by checking for the pagesize of userspace vma before creating
> PMD hugepage at stage 2.
>
> Fixes: ad361f093c1e31d ("KVM: ARM: Support hugetlbfs backed huge pages")
> Signed-off-by: Punit Agrawal <punit.agrawal@xxxxxxx>
> Cc: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
> Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> virt/kvm/arm/mmu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
> index b4b69c2d1012..9dea96380339 100644
> --- a/virt/kvm/arm/mmu.c
> +++ b/virt/kvm/arm/mmu.c
> @@ -1310,7 +1310,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> return -EFAULT;
> }
>
> - if (is_vm_hugetlb_page(vma) && !logging_active) {
> + if (vma_kernel_pagesize(vma) == PMD_SIZE && !logging_active) {
Don't we need to also fix this in kvm_send_hwpoison_signal?
(which probably implies this will then need a backport without that for
older stable kernels. Has this been an issue from the start or did we
add contiguous hugepage support at some point?)
> hugetlb = true;
> gfn = (fault_ipa & PMD_MASK) >> PAGE_SHIFT;
> } else {
> --
> 2.15.1
>
Thanks,
-Christoffer
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